Brooks Instrument Mfi Series - Manual (Page 9)

1-1
Section 1 Introduction
Brooks ® Mf Series
Installation and Operation Manual
X-TMF-Mfi-Mfx-MFC-eng
Part Number: 541B074AAG
August, 2009
1-1 Description
The Brooks ® Mf TM Series mass flow controllers and meters are specifically
designed to be used in an industrial environment. These controllers and
meters offer high accuracy, control and measurement of industrial gases
with the added integrity of NEMA 4X, IP66 industrial packaging. The heart
of the controller and meter is the flow sensor which produces an electrical
output signal linear with mass flow rate. This output can be used for
indicating, recording and/or control purposes. The Brooks Mf Series Mass
Flow Controller has an integral valve and accepts a remote setpoint which
makes it a simple and easy to install flow control system. Many options are
offered to provide a versatile system of mass flow control and
measurement.
1-2 Design Features
• NEMA 4X, IP66 watertight construction
• UL and cUL listed and recognized for
Class1 Division 2 hazardous locations (Mfx )
• Wide FS flow range for measurement and control
for gases from 3 sccm to 1000 slpm N
2
(control)
and 1000 slpm N
2
( measurement)
Flow control to 1000 slpm N
2
Flow metering to 1000 slpm N
2
• Sensor: Removable (Mfi) / Welded (Mfx)
• Insensitive to mounting attitude
• Selectable response time
• Electrically activated valve override
• Low command flow cutoff
• Corrosion resistant valve
1-3 Principle of Operation
The operating principle of the Brooks mass flow controller and meter is
thermodynamic. A wire wound heating element directs heat to the midpoint
of the bypass sensor tube. A predetermined portion of the total flow, flows
through the bypass sensor tube. On the same tube, equidistant upstream
and downstream of the heat input, are resistance temperature measuring
elements.
With no flow, the heat reaching each temperature element is equal. With
increasing flow the flow stream carries heat away from the upstream
element, T1, and an increasing amount towards the downstream element,
T2. An increasing temperature difference develops between the two
elements and this difference is proportional to the amount of gas flowing or
the mass flow rate. A bridge circuit interprets the temperature difference